Fatty acids are one of the principal components of lipids. In vivo, fatty acids are bonded to glycerin via an ester bond to form lipids such as triacylglycerol. Further, many animals and plants also store and utilize fatty acids as an energy source. These fatty acids and lipids stored in animals and plants are widely utilized for food or industrial use.
For example, higher alcohol derivatives that are obtained by reducing higher fatty acids having approximately 12 to 18 carbon atoms are used as surfactants. Alkyl sulfuric acid ester salts, alkylbenzenesulfonic acid salts and the like are utilized as anionic surfactants. Further, polyoxyalkylene alkyl ethers, alkyl polyglycosides and the like are utilized as nonionic surfactants. These surfactants are used for detergents or disinfectants. Other higher alcohol derivatives, such as alkylamine salts and mono- or dialkyl-quaternary amine salts are commonly used for fiber treatment agents, hair conditioning agents or disinfectants. Moreover, benzalkonlum type quaternary ammonium salts are commonly used for disinfectants or antiseptics. Furthermore, higher alcohols having approximately 18 carbon atoms are also useful as a growth promoter for a plant.
Fatty acids and lipids are widely used for various applications shown above, and therefore, it has been attempted to enhance the productivity of fatty acids or lipids in vivo by using plants and the like. Furthermore, the applications and usefulness of fatty acids depend on the number of carbon atoms. Therefore, controlling of the number of carbon atoms of the fatty acids, namely, a chain length thereof has also been attempted. For example, a method of accumulating fatty acids having 12 carbon atoms by introducing an acyl-ACP (acyl carrier protein) thioesterase derived from Umbellularia californica (California bay) (Patent Literature 1, and Non-Patent Literature 1) has been proposed.
Recently, algae attract attention due to its usefulness in biofuel production. The algae can produce lipids that can be used as the biodiesel fuels through photosynthesis, and do not compete with foods. Therefore, the algae attract attention as next-generation biomass resources. Moreover, the algae are also reported to the effect that the algae have higher lipid productivity and accumulation ability in comparison with plants.
Research has started on a lipid synthesis mechanism of the algae and lipid production technologies utilizing the mechanism, but unclear parts remain in many respects. For example, almost no report has been made so far on the above-mentioned acyl-ACP thioesterase derived from algae, either, and only limited examples of reports are made on Class Diatomea or the like (for example, Non-Patent Literature 2).